A series of indole derivatives related to tryptophan reacted with the osmium tetraoxide-pyridine reagent to form bis(pyridine)osmate esters by addition to the 2,3-position of the indole ring. l-Methyl-a-A'-acetyl-DLtryptophan formed a pair of easily separable diastereomeric esters. A study of the kinetics of these reactions showed the expected first-order dependence on osmium tetraoxide and on the indole component. The dependence on pyridine, however, varied with the structure of the indole. Those 3-indolyl derivatives with a threeor four-carbon side chain terminating in a carboxyl group showed an apparent pyridine dependence close to first order. Other

. Can. J. Chem. 59,451 (1981). The effects of hydrogen bonding and protonation produced by changing solvent from chloroform to 2,2,2-trifluoroethanol to trifluoroacetic acid were determined for the 13C chemical shifts of fourteen imines, four oximes, and two pyridines. Downfield shifts relative to chloroform were observed for the C=N carbon of the imines and oximes in both trifluoroethanol and trifluoroacetic acid, ranging from 1.5 to 27.5 ppm, which contrasts with upfield C, shifts for the pyridines in trifluoroacetic acid. Substantial downfield and upfield shifts of from +10 to -15 ppm were found for the para and ipso carbons, respectively, of the aromatic rings attached to the C=N group in trifluoroacetic acid. Possible explanations of these shift changes are considered as well as their relation to the corresponding changes in 15N shifts with the identical variations in solvent.MALWINA ALLEN et JOHN D. ROBERTS. Can. J. Chem. 59,451 (1981). Utilisant le chloroforme, la trifluoro-2,2,2 ethanol et I'acide trifluoroacetique comme solvants, on a determine les effets de la liaison hydrogtne et de la protonation resultant du changement de solvant sur les deplacements chimiques du 13C de 14 imines, de 4 oximes et de deux pyridines. On a observe des deplacements chimiques vers les champs faibles (allant de 1,s a 27,s ppm) du carbone C=N des imines et des oximes dans le trifluoroethanol et dans I'acide trifluoroacetique; ces resultats contrastent avec les deplacements chimiques vers les champs forts observes pour les C, des pyridines dans I'acide trifluoroac8tique. Dans I'acide trifluoroacetique, on aobservt des deplacements importantsvers les champsfaibles et vers les champsforts allantde +10 a -15 ppm pour les carbones respectivement en positionspara et ipso des cycles aromatiques lies au groupe C=N.On considere des explications probables de ces deplacements aussi bien que leur relation avec les changements correspondants dans les deplacements chimiques du 15N avec des changements identiques de solvants.[Traduit par le journal]

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